FUNCTIONS OF THE CIRCULATORY SYSTEM
Carries blood.
Exchanges nutrients, waste products, and gases with tissues.
Transports substances.
Helps regulate blood pressure.
Directs blood flow to the tissues.
Blood vessels outside the heart are divided into
pulmonary vessels systemic vessels
GENERAL FEATURES OF BLOOD VESSEL STRUCTURE
• Arteries • Arterioles • Veins • Venules • Capillaries
Tunics:
• tunica intima • tunica media • tunica adventitia
Elastic arteries
-the largest-diameter arteries and have the thickest walls -greater proportion of their walls is composed of elastic tissue, and a smaller proportion is smooth muscle -examples: aorta and pulmonary trunk
Muscular arteries
include medium-sized and small arteries
walls are relatively thick compared to their diameter
most of the wall’s thickness results from smooth muscle cells of the tunica media
frequently called distributing arteries
Arterioles
transport blood from small arteries to capillaries
smallest arteries in which the three tunics can be identified
Capillaries
• branch of to form networks • regulated by smooth muscle cells called precapillary sphincters • capillary walls consist of endothelium, which is a layer of simple squamous epithelium
Veins
Venules Small veinsMedium-sized veins Large veins
valves
ensure that blood flows toward the heart but not in the opposite direction
BLOOD VESSELS OF THE PULMONARY CIRCULATION
pulmonary trunk pulmonary arteries pulmonary veins(four; two from each lung)
Varicose veins
result when the veins of the lower limbs become so dilated that the cusps of the valves no longer overlap to prevent the backflow of blood
Thromboses
occurs when blood clots block veins
Phlebitis
inflammation of veins
Gangrene
death of body tissue due to a lack of blood flow or a serious bacterial infection
Aorta
largest artery; originates from the left ventricle
Divisions of aorta:
• Ascending aorta • Aortic arch • Descending aorta o Thoracic aorta o Abdominal aorta
Brachiocephalic artery
1st branch from aortic arch
Right common carotid artery
medial branch of the brachiocephalic artery; transports blood to the right side of the head and neck
Right subclavian artery
lateral branch of the brachiocephalic artery; transports blood to the right upper limb
Left common carotid artery
2nd branch of aortic arch; transports blood to the left side of the head and neck
Left subclavian artery
3rd branch of aortic arch;transports blood to the left upper limb
Internal and External Carotid Artery
branches of common carotid artery
Internal carotid artery
enter the brain to become circle of Willis
Circle of Willis
circular system of arteries around the brain’s base which keeps the brain oxygenated
Arteries of the Upper Limb
• Axillary artery • Brachial artery • Ulnar artery • Radial artery
Thoracic aorta
o Visceral arteries o Parietal arteries
Intercostal artery
provide blood to the intercostal muscles
Phrenic artery
provide blood to the diaphragm
Abdominal Aorta and Its Branches
• Visceral arteries Unpaired: o Celiac artery o Superior mesenteric artery o Inferior mesenteric artery Paired: o Renal artery o Suprarenal artery o Gonadal artery • Parietal arteries o inferior phrenic arteries o lumbar arteries o median sacral artery -
Arteries of the Pelvis
• Common iliac o Internal iliac o External iliac
Femoral artery
from external iliac and supplies the thigh
Popliteal artery
from femoral and supplies the posterior knee
Anterior and posterior tibial artery
from femoral and supplies shin area
Dorsalis pedis artery
from the anterior tibial
Fibular artery
aka peroneal artery; from posterior tibial artery; supplies the lateral ed and foot
BLOOD VESSELS OF THE SYSTEMIC CIRCULATION: VEINS
Superior vena cava -returns blood from the head, neck, thorax, and upper limbs to the right atrium of the heart
Inferior vena cava -returns blood from the abdomen, pelvis, and lower limbs to the right atrium
Brachiocephalic vein
drains into the SVC
Subclavian vein
lateral branch which drains into the brachiocephalic
Internal jugular vein
medial branch which drains into the brachiocephalic
External jugular vein
external vein of the neck and is the lateral branch which drains into subclavian
Axillary vein
medial branch which drains into the subclavian
Brachial vein
superficial vein which drains into the axillary
Cephalic vein
lateral branch which drains into the subclavian
Basilic vein
becomes the axillary vein; major superficial veins
Median cubital vein
usually connects the cephalic vein or its tributaries with the basilic vein
Veins of the Thorax
• Azygos vein • Hemiazygos vein • Intercostal vein
Common iliac vein
2 branches that join together to become the IVC; receives blood from lower extremities and brings it back to IVC
External iliac vein
receives all the blood from lower extremities; drains blood into the common iliac
Femoral vein
major lateral branch into the external iliac
Great saphenous vein
major medial branch into the external iliac
Popliteal vein
drains the posterior knee and drains into the femoral
Small saphenous
lateral branch draining to the popliteal
Anterior/Posterior Tibial
draining to the popliteal
pulmonary vessels
transport blood from the right ventricle of the heart through the lungs and back to the left atrium
systemic vessels
transport blood from the left ventricle of the heart through all parts of the body and back to the right atrium
Arteries
blood vessels that conduct blood away from the heart; usually carry oxygenated blood
Arterioles
small artery that leads to a capillary
Veins
blood vessels that brings blood back to the heart; usually carry deoxygenated blood
Venules
small vein that leads to a capillary
Capillaries
small network of vessels where air exchange happens
tunica intima
innermost layer, consists of an endothelium composed of simple squamous epithelial cells
tunica media
middle layer, consists of smooth muscle cells arranged circularly around the blood vessel
tunica adventitia
composed of dense connective tissue adjacent to the tunica media; becomes loose connective tissue toward the outer portion
Venules
have a diameter slightly larger than that of capillaries
Small veins
o slightly larger in diameter than venules o all three tunics are present
Medium-sized veins
o collect blood from small veins and deliver it to large veins o have three thin but distinctive tunics
Large veins
also have three thin but distinctive tunics
pulmonary trunk
branches into right and left pulmonary arteries
pulmonary arteries
extend to the right and left lungs; carry deoxygenated blood to the pulmonary capillaries in the lungs
pulmonary veins
exit the lungs and carry oxygenated blood to the left atrium
Ascending aorta
from the left ventricles, it goes upward; where coronary arteries branch off
Aortic arch
bend of the aorta
Descending aorta
longest part of the aorta; extends through the thorax and abdomen to the upper margin of the pelvis
Thoracic aorta
portion of the aorta in the thorax
Abdominal aorta
part of the descending aorta within the abdomen
Axillary artery
continuation of the subclavian artery inferior to the clavicle
Brachial artery
continuation of the axillary artery in the upper arm
Ulnar artery
medial branch of the brachial artery
Radial artery
lateral branch of the brachial artery
Visceral arteries
supply the thoracic organs
Parietal arteries
supply the thoracic wall
Celiac artery
to the stomach, pancreas, liver
Superior mesenteric artery
small and proximal large intestine
Inferior mesenteric artery
distal large intestine
Renal artery
to the kidneys
Suprarenal artery
to the adrenals
Gonadal artery
testicular and ovarian
inferior phrenic arteries
supply the diaphragm
lumbar arteries
supply the lumbar vertebrae and back muscles
median sacral artery
median sacral artery
Common iliac
goes to the lower extremity
Internal iliac
medial branch of common iliac; provides blood to the pelvic organs
External iliac
lateral branch of common iliac; goes down to the lower limb
Azygos vein
only found on the left side of the body; unpaired branch which drains into the SVC
Hemiazygos vein
2 sets of multiple veins that empty into the azygos
Intercostal vein
drains into azygos (left) and hemiazygos (right)
Internal iliac vein
2 branches that join together to become the IVC; drains blood from the pelvic area and brings it back to IVC
Portal system
a system of blood vessels that begins and ends with capillary beds and has no pumping mechanism
Inferior mesenteric vein
empties into the splenic vein